Apparatus and method for driving capacitance-type actuator

ABSTRACT

According to one embodiment, a apparatus for driving a capacitance-type actuator includes a first voltage source, a second voltage source, and a driver. The first voltage source outputs a first voltage to charge the capacitance-type actuator. The second voltage source outputs a second voltage to charge the actuator. The driver switches between first and second charges and first and second discharges. The first charge supplies the first voltage to the actuator. The second charge supplies the sum of the first voltage and the second voltage to the actuator. The first discharge emits a charge accumulated in the actuator and guides the charge to the second voltage source. The second discharge emits the charge accumulated in the actuator without guiding the charge to the second voltage source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2010-273249, filed on Dec. 8,2010, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an apparatus and amethod for driving a capacitance-type actuator used in an inkjet head.

BACKGROUND

The piezoelectric type inkjet head includes many elements that are ofthe capacitance-type actuators as ink ejecting actuators. Therefore, thehigh speed piezoelectric type inkjet head requires a driving device thatdrives the capacitance-type actuators at high speed.

The driving device drives the actuator by passing a forward or reversecurrent through the actuator. The actuator may be charged by the passageof the reverse current after being charged by the passage of the forwardcurrent. Thus, the actuator obtains a degree of vibration correspondingto a voltage level double an output voltage of a DC power supply.

The driving device discharges the voltage at the actuator to near zerowithin a period between the charging performed by the passage of theforward current and the charging performed by the passage of the reversecurrent. When the discharge period is inserted between the chargingperiod of the passage of the forward current and the charging period ofthe passage of the reverse current, power consumption becomes a halfcompared with the case in which a transition is immediately made to thecharging performed by the passage of the reverse current from thecharging performed by the passage of the forward current or the case inwhich the actuator is charged only by the passage of the unidirectionalcurrent using a value double the output voltage.

However, power consumption in the case including the discharge period isreduced up to a half of the power consumption in the case not includingthe discharge period. In order to further reduce the power consumptionin the case including the discharge period, it is necessary to increasethe number of power supplies to perform the multi-stage discharge.However, in such cases, although the power consumption is reduced,unfortunately a configuration of the driving device becomes complicated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a driving device according to a firstembodiment;

FIG. 2 is a view illustrating a data table used by a switch controllerof the first embodiment;

FIG. 3 is a view illustrating an operation pattern of the driving deviceof the first embodiment in performing a first sequence mode;

FIG. 4 is a view illustrating an operation pattern of the driving deviceof the first embodiment in performing a second sequence mode;

FIG. 5 is a view illustrating an operation pattern of the driving deviceof the first embodiment in performing a third sequence mode;

FIG. 6 is a view illustrating an operation pattern of the driving deviceof the first embodiment in performing a fourth sequence mode;

FIG. 7 is a circuit diagram of a driving device according to a secondembodiment;

FIG. 8 is a view illustrating a data table used by a switch controllerof the second embodiment;

FIG. 9 is a view illustrating an operation pattern of the driving deviceof the second embodiment in performing the first sequence mode;

FIG. 10 is a view illustrating an operation pattern of the drivingdevice of the second embodiment in performing the second sequence mode;

FIG. 11 is a view illustrating an operation pattern of the drivingdevice of the second embodiment in performing the third sequence mode;

FIG. 12 is a view illustrating an operation pattern of the drivingdevice of the second embodiment in performing the fourth sequence mode;

FIG. 13 is a circuit diagram of a driving device according to a thirdembodiment;

FIG. 14 is a view illustrating a data table used by a switch controllerof the third embodiment;

FIG. 15 is a view illustrating an operation pattern of the drivingdevice of the third embodiment in performing the first sequence mode;

FIG. 16 is a view illustrating an operation pattern of the drivingdevice of the third embodiment in performing the second sequence mode;

FIG. 17 is a view illustrating an operation pattern of the drivingdevice of the third embodiment in performing the third sequence mode;

FIG. 18 is a view illustrating an operation pattern of the drivingdevice of the third embodiment in performing the fourth sequence mode;

FIG. 19 is a view illustrating an operation pattern of the drivingdevice of the third embodiment in performing a fifth sequence mode;

FIG. 20 is a view illustrating an operation pattern of the drivingdevice of the third embodiment in performing a sixth sequence mode;

FIG. 21 is a view illustrating an operation pattern of the drivingdevice of the third embodiment in performing a seventh sequence mode;

FIG. 22 is a circuit diagram of a driving device according to a fourthand fifth embodiments;

FIG. 23 is a view illustrating a data table used by a switch controllerof the fourth embodiment;

FIG. 24 is a view illustrating an operation pattern of the drivingdevice of the fourth and fifth embodiments in performing the firstsequence mode;

FIG. 25 is a view illustrating an operation pattern of the drivingdevice of the fourth embodiment in performing the second sequence mode;

FIG. 26 is a view illustrating an operation pattern of the drivingdevice of the fourth embodiment in performing the third sequence mode;

FIG. 27 is a view illustrating an operation pattern of the drivingdevice of the fourth embodiment in performing the fourth sequence mode;

FIG. 28 is a view illustrating an operation pattern of the drivingdevice of the fourth embodiment in performing the fifth sequence mode;

FIG. 29 is a view illustrating an operation pattern of the drivingdevice of the fourth embodiment in performing the sixth sequence mode;

FIG. 30 is a view illustrating a data table used by a switch controllerof the fifth embodiment;

FIG. 31 is a view illustrating an operation pattern of the drivingdevice of the fifth embodiment in performing the second sequence mode;

FIG. 32 is a view illustrating an operation pattern of the drivingdevice of the fifth embodiment in performing the third sequence mode;

FIG. 33 is a view illustrating an operation pattern of the drivingdevice of the fifth embodiment in performing the fourth sequence mode;and

FIG. 34 is a view illustrating an operation pattern of the drivingdevice of the fifth embodiment in performing the fifth sequence mode.

DETAILED DESCRIPTION

In general, according to one embodiment, an apparatus for driving acapacitance-type actuator includes a first voltage source, a secondvoltage source, and a driver. The first voltage source outputs a firstvoltage to charge the capacitance-type actuator. The second voltagesource outputs a second voltage to charge the actuator. The driverswitches between first and second charges and first and seconddischarges. The first charge supplies the first voltage to the actuator.The second charge supplies the sum of the first voltage and the secondvoltage to the actuator. The first discharge emits a charge accumulatedin the actuator and guides the charge to the second voltage source. Thesecond discharge emits the charge accumulated in the actuator withoutguiding the charge to the second voltage source.

The driving device of the capacitance-type actuator used in the inkjethead will be described below with reference to the drawings.

First Embodiment

A first embodiment will be described with reference to FIGS. 1 to 6.

FIG. 1 is a circuit diagram of a driving device 100 of the firstembodiment. As illustrated in FIG. 1, the driving device 100 includes aDC power supply 1, a capacitor 2, plural switches S1, S2, S3, S4, S5,S6, S7, S8, S9, S10, . . . , plural actuators Z1, Z2, Z3, . . . , and aswitch controller 13.

The DC power supply 1 outputs DC voltage E/2. The switch controller 13switches between turn-on and turn-off of each of the switches S1, S2,S3, S4, S5, S6, S7, S8, S9, and S10.

In the driving device 100, a first terminal of the capacitor 2 isconnected to a positive electrode of the DC power supply 1 while theswitches S1 and S2 are series-connected therebetween, and a secondterminal of the capacitor 2 is connected to a negative electrode of theDC power supply 1 through the switch S3. In the driving device 100, aconnection point of the switch S2 and the capacitor 2 is connected tothe negative electrode of the DC power supply 1 through the switch S4.

In the driving device 100, a series circuit of the switches S5 and S6, aseries circuit of the switches S7 and S8, a series circuit of theswitches S9 and S10, . . . are sequentially parallel-connected betweenthe connection point of the switches S1 and S2 and the connection pointof the switch S3 and the capacitor 2. The capacitance-type actuators Z1,Z2, Z3, . . . are connected among the series circuits of the switches.That is, electrodes of actuators Z1, Z2, Z3, . . . are series-connected.

Capacitances of actuators Z1, Z2, Z3, . . . are substantially equal toone another. The capacitance of the capacitor 2 is sufficiently largerthan the sum of the capacitances of the actuators that cansimultaneously be driven in actuators Z1, Z2, Z3, . . . .

The DC power supply 1 outputs the first voltage to charge actuators Z1,Z2, Z3, . . . (the first voltage source). The capacitor 2 outputs thesecond voltage to charge actuators Z1, Z2, Z3, . . . (the second voltagesource).

A circuit 11 including the switches S1, S2, S3, and S4 is a charging ordischarging current-carrying path common to actuators Z1, Z2, Z3, . . .. A circuit 12 including the switches S5, S6, S7, S8, S9, S10, . . . isa charging or discharging current-carrying path for each of actuatorsZ1, Z2, Z3, . . . .

In the circuit 11, when the switches S1, S2, and S3 are turned on whilethe switch S4 is turned off, the capacitor 2 is parallel-connected tothe DC power supply 1. Therefore, the capacitor 2 is charged by voltageE/2 of the DC power supply 1. When the switches S1 and S4 are turned onwhile the switches S2 and S3 are turned off, the capacitor 2 isseries-connected to the DC power supply 1. Therefore, voltage E doublevoltage E/2 output from the DC power supply 1 is supplied to the circuit12. That is, the circuit 11 acts as a charge pump.

In this embodiment, the inkjet head is a shear-mode, shared-wall type.In this kind of inkjet head, one ink channel includes a set of inkchamber and a nozzle. When the ink is ejected from the nozzle of one inkchannel, the two actuators that sandwich the ink channel are operated.That is, one actuator is shared as the ink ejecting actuator by twoadjacent ink channels. The electrode that connects ends of the twoadjacent actuators corresponds to one ink channel.

An actuator is operated when electrodes at both ends of the actuator areenergized. Accordingly, when the ink is ejected from one nozzle, notonly the ink channel of the nozzle but also the two ink channels on boththe sides thereof are driven. For the sake of convenience, in thesethree ink channels, the ink channel corresponding to the nozzle thatshould eject the ink is referred to as a center ink channel, and othertwo ink channels are referred to as adjacent ink channels.

Operations of charging and discharging adjacent actuators Z1 and Z2necessary to eject the ink from the nozzle of the center ink channelwill be described.

Generally it is possible to design two kinds of actuators, namely, afirst-type actuator and a second-type actuator. In the first-typeactuator, the ink chamber of the center ink channel is operated in anexpansion direction when the positive voltage is applied to the centerink channel while the negative voltages are applied to the adjacent inkchannels, and the ink chamber of the center ink channel is operated in acontraction direction when the negative voltage is applied to the centerink channel while the positive voltages are applied to the adjacent inkchannels. In the second-type actuator, the ink chamber of the center inkchannel is operated in a reverse manner. Hereinafter, the case in whichthe first-type actuators are used will be described. In the case inwhich the second-type actuators are used, the direction in whichactuators Z1 and Z2 are charged may be inverted with respect to thefirst-type actuator. That is, in the case in which the second-typeactuators are used, the methods for driving the center ink channel andthe adjacent ink channels should be replaced with each other.

In order to eject the ink from one nozzle that uses actuators Z1 and Z2,the switch controller 13 switches between the turn-on and the turn-offof each of the switches S1, S2, S3, S4, S5, S6, S7, S8, S9, and S10according to a data table 10 of FIG. 2. The switch controller 13includes a logic circuit. The switch controller 13 may include amicrocomputer.

In the driving device 100, the turn-on and the turn-off of selectedswitch result in charging or discharging the adjacent actuators Z1 andZ2.

A first sequence mode M1 charges actuators Z1 and Z2. That is, theswitch controller 13 turns on the switches S1, S2, S3, S6, S7, and S10and turns off the switches S4, S5, S8, and S9.

Therefore, first, second, and third closed circuits are formed asillustrated in FIG. 3. The first closed circuit connects the positiveelectrode and the negative electrode of the DC power supply 1 throughthe switches S1 and S2, the capacitor 2, and the switch S3. The secondclosed circuit connects the positive electrode and the negativeelectrode of the DC power supply 1 through the switches S1 and S7,actuator Z1, and the switches S6 and S3. The third closed circuitconnects the positive electrode and the negative electrode of the DCpower supply 1 through the switches S1 and S7, actuator Z2, and theswitches S10 and S3.

Accordingly, in a charge Q+Qs output from the DC power supply 1, acharge Qs is supplied to the capacitor 2 by the first closed circuit.Charge Q/2 is supplied to each actuators Z1 and Z2 by the second andthird closed circuits, respectively. As a result, the capacitor 2 ischarged by DC voltage E/2. Similarly actuators Z1 and Z2 are charged byDC voltage E/2.

A second sequence mode M2 further charges actuators Z1 and Z2. That is,the switch controller 13 turns on the switches S1, S4, S6, S7, and S10and turns off the switches S2, S3, S5, S8, and S9.

Thus, fourth and fifth closed circuits are formed as illustrated in FIG.4. The fourth closed circuit connects the positive electrode and thenegative electrode of the DC power supply 1 through the switches S1 andS7, actuator Z1, the switch S6, the capacitor 2, and the switch S4. Thefifth closed circuit connects the positive electrode and the negativeelectrode of the DC power supply 1 through the switches S1 and S7,actuator Z2, the switch S10, the capacitor 2, and the switch S4.

Accordingly, a half of a charge Qc output from the DC power supply 1 issupplied to actuators Z1 and Z2 by the fourth and fifth closed circuits,respectively. Charge Qc is emitted from the capacitor 2 charged by DCvoltage E/2.

The capacitance of the capacitor 2 is sufficiently larger than the sumof the capacitances of the actuators that can simultaneously be drivenin actuators Z1, Z2, Z3, . . . . Therefore, even if charge Qc is emittedfrom the capacitor 2, the charge voltage of the capacitor 2 issubstantially maintained at DC voltage E/2. Accordingly, actuators Z1and Z2 are charged by voltage E double DC voltage E/2 output from the DCpower supply 1.

When the adjacent actuators Z1 and Z2 are charged up to voltage E, theink chamber of the ink channel that uses actuators Z1 and Z2 are enoughexpanded from a steady state. As a result, the ink is refilled into theink chamber.

When the ink chamber is expanded, a pressure at the ink chamber istentatively decreased. Then the ink is refilled to increase the pressureat the ink chamber. The expansion state of the ink chamber is maintaineduntil the pressure at the ink chamber becomes a predetermined level(generally becomes the maximum). The transition is made to a nextsequence when the pressure at the ink chamber becomes the predeterminedlevel.

A third sequence mode M3 discharges actuators Z1 and Z2. That is, theswitch controller 13 turns on the switches S2, S6, S7, and S10 and turnsoff the switches S1, S3, S4, S5, S8, and S9.

Therefore, sixth and seventh closed circuits are formed as illustratedin FIG. 5. The sixth closed circuit connects the positive electrode andthe negative electrode of actuator Z1 through the switches S7 and S2,the capacitor 2, and the switch S6. The seventh closed circuit connectsthe positive electrode and the negative electrode of actuator Z2 throughthe switches S7 and S2, the capacitor 2, and the switch S10.

At the start of this sequence, actuators Z1 and Z2 are charged by DCvoltage E while the capacitor 2 is changed by DC voltage E/2. Therefore,actuators Z1 and Z2 discharge a charge Qz/2, respectively. As a result,the capacitor 2 is charged by charge Qz that is of the sum of chargesQz/2.

The capacitance of the capacitor 2 is sufficiently larger than the sumof the capacitances of the actuators that can simultaneously be drivenin actuators Z1, Z2, Z3, . . . . Therefore, even if charge Qz is chargedto the capacitor 2, the charge voltage of the capacitor 2 issubstantially maintained at voltage E/2. Accordingly, actuators Z1 andZ2 are discharged to voltage E/2.

As a result each of change Qz/2 which is discharged from actuators Z1and Z2 is equal to Qc/2 and charge Qz by which the capacitor 2 ischarged is equal to charge Qc that is emitted from the capacitor 2 inthe last second sequence mode M2.

A fourth sequence mode M4 further discharges actuators Z1 and Z2. Thatis, the switch controller 13 turns on the switches S1, S2, S3, S6, S8,and S10 and turns off the switches S4, S5, S7, and S9.

Therefore, eighth, ninth and first closed circuits are formed asillustrated in FIG. 6. The eighth closed circuit connects the positiveelectrode and the negative electrode of actuator Z1 through the switchesS8 and S6. The ninth closed circuit connects the positive electrode andthe negative electrode of actuator Z2 through the switches S8 and S10.

At the start of this sequence, charge voltage E/2 remains in actuatorsZ1 and Z2. Therefore, each of actuators Z1 and Z2 discharges a remainingcharge (Q+Qc−Qz)/2 to become charge voltage 0 (V). As a result, the inkchamber of the ink channel that uses actuators Z1 and Z2 is restoredfrom the expansion state to the steady state. When the ink chamber isrestored to the steady state, the ink in the ink chamber is ejected fromthe corresponding nozzle.

In the meanwhile, the capacitor 2 is adjusted to charge voltage E/2 bythe first closed circuit.

The fourth sequence mode M4 is the final sequence of the ejectionoperation and the steady state of the driving circuit. In the steadystate, the charge voltages of actuators Z1 and Z2 become 0 (V) and thecharge voltage of the capacitor 2 becomes E/2. Therefore, when thetransition is made to the next first sequence mode M1 to drive actuatorsZ1 and Z2, charge Qs that should charge the capacitor 2 usually becomessubstantial 0.

The switches S1, S2, S3, S4, S5, S6, S7, S8, S9, and S10 are thus turnedon and off according to the series of charging or discharging sequencesof the first to fourth sequence modes M1 to M4 described above.Therefore, the adjacent actuators Z1 and Z2 are charged or discharged.The ink is ejected from the nozzle that uses actuators Z1 and Z2 by thecharging and discharging.

In this series of sequences, charge Qc that is emitted from thecapacitor 2 in the second sequence mode M2 is equal to charge Qz that isfed back to the capacitor 2 in the third sequence mode M3.

Accordingly, the power is not take out of the second voltage source.Therefore, it is not necessary to provide a circuit that supplies thepower to the capacitor 2 of the second voltage source.

Additionally, the DC power supply 1 of the first voltage source mayoutput voltage E/2 that is half the maximum voltage E necessary foractuators Z1, Z2, Z3, . . . . Accordingly, the power consumption of thedriving device 100 is reduced to a substantial half of the drivingdevice that is charged once to E.

Above described method of ejecting the ink is such a manner as, 1)expending the chamber, 2) waiting the pressure to be increased, and then3) setting the chamber back to the original state. But the ink ejectingmethod is not limited to the first embodiment.

For example, after the fourth sequence mode M4, the ink chamber can becontracted after waiting for the pressure to be decreased. Then the inkchamber should be returned at the appropriate timing. The appropriateadditional sequence improves sharpness of the ejected ink droplet andreduces the unwanted vibration of the pressure after ejecting the ink.Alternatively, after the discharge of the fourth sequence mode M4, theink chamber can be immediately contracted without waiting for thedecrease in pressure, for the purpose of increasing the speed and volumeof the ink ejection, and then returned at the appropriate timing.

In order to contract the volume of the ink chamber and then return tothe original volume of the ink chamber in accordance with the additionalsequence afore mentioned above, the charge directions of actuators Z1and Z2 may be inverted in the first to fourth sequence modes M1 to M4.That is, the center ink channel driving method and the adjacent inkchannel driving method may be replaced with each other.

In all of the driving methods described above, charge Qc emitted fromthe second voltage source is matched with charge Qz fed back to thesecond voltage source in an interval of the series of sequences ofdriving the actuators. Therefore, the supply of the power to the secondvoltage source is eliminated.

Second Embodiment

A second embodiment will be described with reference to FIGS. 7 to 12.

FIG. 7 is a circuit diagram of a driving device 200 of the secondembodiment. The component in common with that of FIG. 1 is designated bythe same numeral.

FIG. 7 illustrates only circuit elements necessary to drive an actuatorZ1. In the second embodiment, although not illustrated, many actuatorsZ2, Z3, . . . are series-connected similarly to the first embodiment.However, the circuit elements necessary to drive the actuators areidentical to one another. Accordingly, the case in which actuator Z1 ischarged or discharged will be described below. The detailed descriptionsof other actuators Z2, Z3, . . . and the detailed description of the inkejecting operation are omitted.

As illustrated in FIG. 7, the driving device 200 includes a first DCpower supply 1, a capacitor 2, a second DC power supply 21, a diode 22,N-type channel MOS transistors Qcom, Q11, and Q21, P-type channel MOStransistors Q12, Q13, Q22, and Q23, and a switch controller 23.

The switch controller 23 switches between the turn-on and the turn-offof each of MOS transistors Qcom, Q11, Q12, Q13, Q21, Q22, and Q23.

In the second embodiment, the capacitances of actuators Z1, Z2, Z3, . .. are substantially equal to one another. The capacitance of thecapacitor 2 is sufficiently larger than the sum of the capacitances ofthe actuators that can simultaneously be driven in actuators Z1, Z2, Z3,. . . .

The driving device 200 includes first to fourth power supply lines L1,L2, L3, and L4 and a ground line L0 of 0 (V).

The first power supply line L1 is connected to a positive electrode ofthe first DC power supply 1 that outputs DC voltage E/2. The secondpower supply line L2 is connected to the negative electrode of thesecond DC power supply 21 that outputs DC voltage E/2. The positiveelectrode of the second DC power supply 21 is connected to the negativeelectrode of the first DC power supply 1. The ground line L0 isconnected to the connection point of the positive electrode of thesecond DC power supply 21 and the negative electrode of the first DCpower supply 1. Accordingly, the first power supply line L1 becomespotential E/2. The second power supply line L2 becomes potential −E/2.

The ground line L0 is also connected to a source electrode of MOStransistor Qcom. The third power supply line L3 is connected to a drainelectrode of MOS transistor Qcom. The fourth power supply line L4 isconnected to the source electrode of MOS transistor Qcom through thediode 22. In the diode 22, the side to which MOS transistor Qcom isconnected is set to a cathode.

In the driving device 200, the capacitor 2 is connected between thethird power supply line L3 and the fourth power supply line L4. In thedriving device 200, a series circuit of MOS transistors Q13 and Q11 anda series circuit of MOS transistors Q23 and Q21 are connected inparallel to the capacitor 2.

In the series circuit of MOS transistors Q13 and Q11, the drainelectrodes of MOS transistors Q13 and Q11 are connected to each other.The source electrode of MOS transistor Q13 is connected to the thirdpower supply line L3. The source electrode of MOS transistor Q11 isconnected to the fourth power supply line L4.

In the series circuit of MOS transistors Q23 and Q21, the drainelectrodes of MOS transistors Q23 and Q21 are connected to each other.The source electrode of MOS transistor Q23 is connected to the thirdpower supply line L3. The source electrode of MOS transistor Q21 isconnected to the fourth power supply line L4.

In the driving device 200, the drain electrode of MOS transistor Q12 isconnected to the connection point of the drain electrodes of MOStransistors Q13 and Q11. The source electrode of MOS transistor Q12 isconnected to the first power supply line L1.

In the driving device 200, the drain electrode of MOS transistor Q22 isconnected to the connection point of the drain electrodes of MOStransistors Q23 and Q21. The source electrode of MOS transistor Q22 isconnected to the first power supply line L1.

In the driving device 200, the capacitance-type actuator Z1 is connectedbetween the connection point of the drain electrodes of MOS transistorsQ11, Q12, and Q13 and the connection point of the drain electrodes ofMOS transistors Q21, Q22, and Q23.

In the N-type channel MOS transistors Qcom, Q11, and Q21, a back gate ofMOS transistor Qcom is connected to the ground line L0. The back gatesof MOS transistors Q11 and Q21 are connected to the second power supplyline L2 having potential −E/2.

The back gates of the P-type channel MOS transistors Q12, Q13, Q22, andQ23 are connected to the first power supply line L1 having potentialE/2.

The first DC power supply 1 outputs the first voltage to charge actuatorZ1 (the first voltage source). The capacitor 2 outputs the secondvoltage to charge actuator Z1 (the second voltage source).

A circuit 24 including the diode 22 and MOS transistor Qcom is acharging or discharging common current-carrying path with respect toactuators Z1, Z2, Z3, . . . , though in FIG. 7, only the actuator Z1 isillustrated. A circuit 25 including MOS transistors Q11, Q12, Q13, Q21,Q22, and Q23 is a charging or discharging individual current-carryingpath with respect to actuator Z1.

In the circuit 24, when MOS transistors Q12 and Q13 are turned on whileMOS transistor Qcom is turned off, the diode 22 is turned on toparallel-connect the first DC power supply 1 and the capacitor 2.Therefore, the capacitor 2 is charged. The same holds true for the casein which MOS transistors Q22 and Q23 are turned on or for the case inwhich MOS transistors Q12, Q13, Q22, and Q23 are turned on.

On the other hand, when MOS transistor Qcom is turned on while the powersupply line L3 is not connected to another power supply line, the diode22 is cut off to series-connect the DC power supply 1 and the capacitor2. Therefore, voltage E which is double the voltage of E/2 of the DCpower supply 1 is supplied between the first power supply line L1 andthe fourth power supply line L4. That is, the circuit 24 acts as acharge pump.

The gates of MOS transistors Qcom, Q11, Q12, Q13, Q21, Q22, and Q23 areconnected to the switch controller 23. The switch controller 23 switchesbetween the turn-on and the turn-off of each of MOS transistors Qcom,Q11, Q12, Q13, Q21, Q22, and Q23 according to a data table 20 of FIG. 8.The switch controller 23 includes a logic circuit. The switch controller23 may include a microcomputer.

In the driving device 200, the turn-on and the turn-off of each of MOStransistors Qcom, Q11, Q12, Q13, Q21, Q22, and Q23 perform a series ofcharging or discharging sequences to actuator Z1.

A first sequence mode M1 charges actuator Z1. The switch controller 23turns on MOS transistors Q11, Q22, and Q23 and turns off MOS transistorsQcom, Q12, Q13, and Q21.

Therefore, as illustrated in FIG. 9, first and second series circuitsare formed between the first power supply line L1 and the ground lineL0. MOS transistor Q22, actuator Z1, MOS transistor Q11, and the diode22 are series-connected in the first series circuit. MOS transistors Q22and Q23, the capacitor 2, and the diode 22 are series-connected in thesecond series circuit.

The first power supply line L1 has potential E/2. The ground line L0 haspotential 0 (V). Accordingly, in a charge Q+Qs output from the first DCpower supply 1, a charge Q is supplied to actuator Z1 through MOStransistor Q22. A charge Qs is supplied to the capacitor 2 through MOStransistors Q22 and Q23. As a result, the capacitor 2 is charged by DCvoltage E/2. Similarly actuator Z1 is charged by DC voltage E/2.

A second sequence mode M2 further charges actuator Z1. The switchcontroller 23 turns on MOS transistors Qcom, Q11, and Q22 and turns offMOS transistors Q12, Q13, and Q21, and Q23.

As illustrated in FIG. 10, the positive electrode of the capacitor 2charged by voltage E/2 becomes potential 0 (V) by the turn-on of MOStransistor Qcom. Therefore, the negative electrode of the capacitor 2becomes potential −E/2. On the diode 22, the cathode has potential 0 (V)and the anode has potential −E/2. Therefore, the diode 22 is not offstate.

As a result, a third series circuit is formed between the first powersupply line L1 and the ground line L0. MOS transistor Q22, actuator Z1,MOS transistor Q11, the capacitor 2, and MOS transistor Qcom areseries-connected in the third series circuit.

Accordingly, a charge Qc output from the positive electrode of the DCpower supply 1 is supplied to the positive electrode of actuator Z1 bythe third series circuit. At the same time, charge Qc is emitted fromthe capacitor 2 charged by DC voltage E/2. Charge Qc is supplied to thenegative electrode of the DC power supply 1 through MOS transistor Qcom.

In this sequence, the negative electrode of actuator Z1 is connected tothe negative electrode of the capacitor 2 through MOS transistor Q11.Therefore, actuator Z1 is charged by voltage E which is double DCvoltage of E/2 output from the DC power supply 1.

A third sequence mode M3 discharges actuator Z1. The switch controller23 turns on MOS transistors Q11 and Q23 and turns off MOS transistorsQcom, Q12, Q13, Q21, and Q22.

Therefore, a tenth closed circuit is formed as illustrated in FIG. 11.The tenth closed circuit connects the positive electrode and thenegative electrode of actuator Z1 through MOS transistor Q23, thecapacitor 2, and MOS transistor Q11.

The capacitor 2 is previously charged by voltage E/2. Accordingly, acharge Qz is emitted from actuator Z1 which had been charged by DCvoltage E, and then the actuator Z1 is discharged down to voltage E/2.

Charge Qz emitted from actuator Z1 charges the capacitor 2.

The capacitance of the capacitor 2 is sufficiently larger than the sumof the capacitances of the actuators that can simultaneously be drivenin actuators Z1, Z2, Z3, . . . . Therefore, even if charges Qc and Qzare emitted or fed back, the charge voltage of the capacitor 2 in thesecond or third sequence mode M2 or M3 is substantially maintained atvoltage E/2.

So, charge Qz fed back to the capacitor 2 is equal to charge Qc that isemitted from the capacitor 2 in the last second sequence mode M2.

A fourth sequence mode M4 further discharges actuator Z1. The switchcontroller 23 turns on MOS transistors Q11 and Q21 and turns off MOStransistors Qcom, Q12, Q13, Q22, and Q23.

Therefore, an eleventh closed circuit is formed as illustrated in FIG.12. The eleventh closed circuit connects the positive electrode and thenegative electrode of actuator Z1 through MOS transistors Q21 and Q11.Accordingly, the charge is further emitted from actuator Z1, andactuator Z1 is discharged down to voltage 0 (V).

Thus, MOS transistors Qcom, Q11, Q12, Q13, Q21, Q22, and Q23 are turnedon and off according to the series of charging or discharging sequencesof the first to fourth sequence modes M1, M2, M3, and M4. Accordingly,actuator Z1 is charged or discharged.

The voltage change on Z1 at each transition between M1, M2, M3, and M4are all the same value of E/2 (V). So Q, Qc, and Qz are the same.

In this embodiment, charge Qs by which the capacitor 2 is charged in thefirst sequence mode M1 becomes smaller as the voltage of capacitor 2just before the first sequence becomes closer to E/2 (V).

In the steady state in which the actuator is not driven, MOS transistorsQcom, Q11, and Q12 should be turned off, and MOS transistors Q12, Q13,Q22, and Q23 should be turned on. Then, the electric conduction state isestablished between the positive electrode of the DC power supply 1 andthe positive electrode of the capacitor 2. In the mean time the electricconduction state is also established between the negative electrode ofthe DC power supply 1 and the negative electrode of the capacitor 2through the diode 22. The charge voltage of the capacitor 2 is steadilymaintained at E/2. As a result, charge Qs substantially becomes zeroexcept the power-on state.

In the second embodiment, charge Qc that is emitted from the capacitor 2in the second sequence mode M2 is equal to charge Qz that is fed back tothe capacitor 2 in the third sequence mode M3. Accordingly, the power isnot take out of the second voltage source. Therefore, it is notnecessary to provide a circuit that supplies the power to the capacitor2 of the second voltage source.

Additionally, the DC power supply 1 of the first voltage source mayoutput voltage E/2 that is half the maximum voltage E necessary foractuators Z1, Z2, Z3, . . . . Accordingly, the power consumption of thedriving device 200 is reduced to a substantial half of the drivingdevice that is charged once to E.

Accordingly, the same effect as the first embodiment is obtained.

The second DC power supply 21 of the second embodiment provides just abias to the back gates of the N-type channel MOS transistors Q11 andQ21. Accordingly, there is no significantly power consumption in thesecond DC power supply 21.

Third Embodiment

A third embodiment will be described with reference to FIGS. 13 to 21.

FIG. 13 is a circuit diagram of a driving device 300 of the thirdembodiment, and only the circuit elements necessary to drive an actuatorZ1 are illustrated in FIG. 13 for the same reason as the secondembodiment. The component in common with that of FIG. 7 is designated bythe same numeral.

As illustrated in FIG. 13, the driving device 300 includes a first DCpower supply 1, a capacitor 2, a second DC power supply 21, N-typechannel MOS transistors Qn, Q11, Q12, Q21, and Q22, P-type channel MOStransistors Qp, Qp2, Q13, and Q23, and a switch controller 31.

The switch controller 31 switches between the turn-on and the turn-offof each of MOS transistors Qp, Qp2, Qn, Q11, Q12, Q13, Q21, Q22, andQ23.

In the third embodiment, the capacitances of actuators Z1, Z2, Z3, . . .are substantially equal to one another. The capacitance of the capacitor2 is sufficiently larger than the sum of the capacitances of theactuators that can simultaneously be driven in actuators Z1, Z2, Z3, . .. .

The driving device 300 includes first to fourth power supply lines L1,L2, L3, and L4 and a ground line L0 of 0 V.

The first power supply line L1 is connected to a positive electrode ofthe first DC power supply 1 that outputs DC voltage E/2. The secondpower supply line L2 is connected to the negative electrode of thesecond DC power supply 21 that outputs DC voltage E/2. The positiveelectrode of the second DC power supply 21 is connected to the negativeelectrode of the first DC power supply 1. The ground line L0 isconnected to the connection point of the positive electrode of thesecond DC power supply 21 and the negative electrode of the first DCpower supply 1. Accordingly, the first power supply line L1 becomespotential E/2 (V). The second power supply line L2 becomes potential−E/2 (V).

In the driving device 300, a series circuit of MOS transistors Qp, Qp2,and Qn is connected between the first power supply line L1 and theground line L0. The source electrode of MOS transistor Qp is connectedto the first power supply line L1. The drain electrode of MOS transistorQp is connected to the source electrode of MOS transistor Qp2. The drainelectrode of MOS transistor Qp2 is connected to the drain electrode ofMOS transistor Qn. The source electrode of MOS transistor Qn isconnected to the ground line L0.

The third power supply line L3 is connected to the connection point ofthe drain electrode of MOS transistor Qp and the source electrode of MOStransistor Qp2. The fourth power supply line L4 is connected to theconnection point of the drain electrode of MOS transistor Qp2 and thedrain electrode of MOS transistor Qn through the capacitor 2.

In the driving device 300, a series circuit of MOS transistors Q13 andQ11 and a series circuit of MOS transistors Q23 and Q21 areparallel-connected between the third power supply line L3 and the fourthpower supply line L4.

In the series circuit of MOS transistors Q13 and Q11, the drainelectrodes of MOS transistors Q13 and Q11 are connected to each other.The source electrode of MOS transistor Q13 is connected to the thirdpower supply line L3. The source electrode of MOS transistor Q11 isconnected to the fourth power supply line L4.

In the series circuit of MOS transistors Q23 and Q21, the drainelectrodes of MOS transistors Q23 and Q21 are connected to each other.The source electrode of MOS transistor Q23 is connected to the thirdpower supply line L3. The source electrode of MOS transistor Q21 isconnected to the fourth power supply line L4.

In the driving device 300, the drain electrode of MOS transistor Q12 isconnected to the connection point of the drain electrodes of MOStransistors Q13 and Q11. The source electrode of MOS transistor Q12 isconnected to the ground line L0.

In the driving device 300, the drain electrode of MOS transistor Q22 isconnected to the connection point of the drain electrodes of MOStransistors Q23 and Q21. The source electrode of MOS transistor Q22 isconnected to the ground line L0.

In the driving device 300, the capacitance-type actuator Z1 is connectedbetween the connection point of the drain electrodes of MOS transistorsQ11, Q12, and Q13 and the connection point of the drain electrodes ofMOS transistors Q21, Q22, and Q23.

The back gate of MOS transistor Qn is connected to the ground line L0.The back gates of MOS transistors Q11, Q12, Q21, and Q22 are connectedto the second power supply line L2.

The second DC power supply 21 provides just the bias to the back gatesof the N-type channel MOS transistors Q11, Q12, Q21, and Q22.Accordingly, there is no significantly power consumption in the secondDC power supply 21.

The back gates of MOS transistors Qp, Q13, and Q23 are connected to thefirst power supply line L1. The back gate of MOS transistor Qp2 isconnected to the third power supply line L3.

The first DC power supply 1 outputs the first voltage to charge actuatorZ1 (the first voltage source). The capacitor 2 outputs the secondvoltage to charge actuator Z1 (the second voltage source).

A circuit 32 including MOS transistor Qp, Qp2, and Qn is a charging ordischarging common current-carrying path with respect to actuators Z1,Z2, Z3, . . . , though in FIG. 13, only the actuator Z1 is illustrated.A circuit 33 including MOS transistors Q11, Q12, Q13, Q21, Q22, and Q23is a charging or discharging individual current-carrying path withrespect to actuator Z1.

In the circuit 32, in the case in which MOS transistors Qp and Qp2 areturned on while MOS transistor Qn is turned off, the first DC powersupply 1 and the capacitor 2 are parallel-connected when the N-typechannel MOS transistors Q11 and Q12 are turned on. Therefore, thecapacitor 2 is charged. The same holds true for the case in which MOStransistors Q21 and Q22 are turned on or for the case in which MOStransistors Q11, Q12, Q21, and Q22 are turned on.

In the case, MOS transistors Qp and Qn are turned on while MOStransistor Qp2 being turned off, the power supply 1 and the capacitor 2are series connected between power supply lines L3 and L4. Therefore,voltage E which is double the voltage of E/2 of the first DC powersupply 1 is supplied between the third power supply line L3 and thefourth power supply line L4. That is, the circuit 32 acts as a chargepump.

The gates of MOS transistors Qp, Qp2, Qn, Q11, Q12, Q13, Q21, Q22, andQ23 are connected to the switch controller 31. The switch controller 31switches between the turn-on and the turn-off of each of MOS transistorsQp, Qp2, Qn, Q11, Q12, Q13, Q21, Q22, and Q23 according to a data table30 of FIG. 14. The switch controller 31 includes a logic circuit. Theswitch controller 31 may include a microcomputer.

In the driving device 300, the turn-on and the turn-off of each of MOStransistors Qp, Qp2, Qn, Q11, Q12, Q13, Q21, Q22, and Q23 perform aseries of charging or discharging sequences to actuator Z1.

A first sequence mode M1 is a waiting state before actuator Z1 ischarged. The switch controller 31 turns on MOS transistors Qp, Qp2, Q11,Q12, Q21, and Q22 and turns off MOS transistors Qn, Q13, and Q23.

Therefore, as illustrated in FIG. 15, a fourth series circuit is formedbetween the first power supply line L1 and the ground line L0. MOStransistors Qp and Qp2, the capacitor 2, and MOS transistors Q11 and Q12are series-connected in the fourth series circuit. Alternatively, MOStransistors Qp and Qp2, the capacitor 2, and MOS transistors Q21 and Q22are series-connected in the fourth series circuit.

The first power supply line L1 has potential E/2 (V). The ground line L0has potential 0 V. Accordingly, a charge Qs output from the first DCpower supply 1 is supplied to the capacitor 2 through MOS transistors Qpand Qp2. As a result, the capacitor 2 is charged by DC voltage E/2 (V).

At this point, the third power supply line L3 is connected to the firstDC power supply 1 through MOS transistor Qp. Accordingly, the thirdpower supply line L3 becomes potential E/2 (V).

A second sequence mode M2 is performed immediately before the chargingof actuator Z1 is started, for example, 1 μs before. The switchcontroller 31 turns on MOS transistors Qp, Qn, and Q12 and turns off MOStransistors Qp2, Q11, Q13, Q21, Q22, and Q23.

As illustrated in FIG. 16, the positive electrode of the capacitor 2 isconnected to the ground line L0 through MOS transistor Qn. Therefore,the negative electrode of the capacitor 2 charged by DC voltage E/2becomes potential −E/2 (V). The negative electrode of actuator Z1 isconnected to the ground line L0. Therefore, the negative electrode ofactuator Z1 becomes potential 0 (V).

A third sequence mode M3 charges actuator Z1. The switch controller 31turns on MOS transistors Qp, Qn, Q12, and Q23 and turns off MOStransistors Qp2, Q11, Q13, Q21, and Q22.

Therefore, as illustrated in FIG. 17, a fifth series circuit is formedbetween the first power supply line L1 and the ground line L0. MOStransistors Qp and Q23, actuator Z1, and MOS transistor Q12 areseries-connected in the fifth series circuit.

The first power supply line L1 has potential E/2 (V). The ground line L0has potential 0 (V). Accordingly, a charge Q output from the first DCpower supply 1 is supplied to actuator Z1 through MOS transistor Q23.Actuator Z1 is charged by DC voltage E/2.

A fourth sequence mode M4 further charges actuator Z1. The switchcontroller 31 turns on MOS transistors Qp, Qn, Q11, and Q23 and turnsoff MOS transistors Qp2, Q12, Q13, Q21, and Q22.

Therefore, as illustrated in FIG. 18, a sixth series circuit is formedbetween the first power supply line L1 and the ground line L0. MOStransistors Qp and Q23, actuator Z1, MOS transistor Q11, the capacitor2, and MOS transistor Qn are series-connected in the sixth seriescircuit.

Therefore, the potential at the negative electrode of actuator Z1 isdecreased from 0 to potential −E/2 at the negative electrode of thecapacitor 2. Accordingly, a charge Qc output from the first DC powersupply 1 is supplied to actuator Z1 through MOS transistor Q23.

At the same time, a charge Qc is emitted from the capacitor 2 charged byDC voltage E/2. Charge Qc is supplied to the first DC power supply 1through MOS transistor Qn. Accordingly, actuator Z1 is charged byvoltage E which is double the DC voltage of E/2 of the first DC powersupply 1.

A fifth sequence mode M5 is performed immediately before actuator Z1 isdischarged, for example, 1 μs before. The switch controller 31 turns onMOS transistors Qp2 and Q11 and turns off MOS transistors Qp, Qn, Q12,Q13, Q21, Q22, and Q23.

As illustrated in FIG. 19, the third power supply line L3 is connectedto the capacitor 2 through MOS transistor Qp2. The circuit including MOStransistor Qp2, the capacitor 2, MOS transistor Q11, and the negativeelectrode of actuator Z1 constitutes a floating circuit. As a result,the potential at the third power supply line L3 starts to decreased fromE/2 (V).

A sixth sequence mode M6 discharges actuator Z1. The switch controller31 turns on MOS transistors Qp2, Q11, and Q23 and turns off MOStransistors Qp, Qn, Q12, Q13, Q21, and Q22.

Therefore, a twelfth closed circuit is formed as illustrated in FIG. 20.The twelfth closed circuit connects the positive electrode and thenegative electrode of actuator Z1 through MOS transistors Q23 and Qp2,the capacitor 2, and MOS transistor Q11.

The capacitor 2 had been charged by voltage E/2. A charge Qz is emittedfrom actuator Z1 which had been charged by DC voltage E.

The capacitance of the capacitor 2 is sufficiently larger than the sumof the capacitances of the actuators that can simultaneously be drivenin actuators Z1, Z2, Z3, . . . . Therefore, even if charges Qc and Qzare emitted or fed back, the charge voltage of the capacitor 2 in thethird or fourth sequence mode M3 or M4 is substantially maintained atvoltage E/2. So, Actuator Z1 is discharged down to voltage E/2 (V).

Charge Qz emitted from actuator Z1 is fed back to the capacitor 2.Charge Qz fed back to the capacitor 2 is equal to charge Qc that isemitted from the capacitor 2 in the last fourth sequence mode M4.

A seventh sequence mode M7 further discharges actuator Z1. The switchcontroller 31 turns on MOS transistors Qp2, Q11, Q12, Q21, and Q22 andturns off MOS transistors Qp, Qn, Q13, and Q23.

Therefore, thirteenth and fourteenth closed circuits are formed asillustrated in FIG. 21. The thirteenth closed circuit connects thepositive electrode and the negative electrode of actuator Z1 through MOStransistors Q21 and Q11. The fourteenth closed circuit connects thepositive electrode and the negative electrode of actuator Z1 through MOStransistors Q22 and Q12.

Accordingly, the charge is further emitted from actuator Z1. Actuator Z1is discharged down to voltage 0 (V). At this point, the fourth powersupply line L4 becomes the same potential as the ground line L0, namely,0. Accordingly, the potential at the third power supply line L3connected to the capacitor 2 through MOS transistor Qp2 becomes E/2 (V),which is the charged voltage of the capacitor 2.

MOS transistors Qp, Qp2, Qn, Q11, Q12, Q13, Q21, Q22, and Q23 are turnedon and off according to the series of charging or discharging sequencesof the first to seventh sequence modes M1, M2, M3, M4, M5, M6, and M7.Accordingly, actuator Z1 is charged or discharged.

In the third embodiment, charge Qs by which the capacitor 2 is chargedin the first sequence mode M1 becomes smaller as the voltage ofcapacitor 2 just before the first sequence becomes closer to E/2 (V).

The driving device 300 returns to the first sequence mode M1 after thedischarge is ended in the seventh sequence mode M7. In the drivingdevice 300, the first sequence mode M1 is set to the steady state.Therefore, the charge voltage of the capacitor 2 is steadily maintainedat E/2. As a result, charge Qs substantially becomes zero except thepower-on state.

In the third embodiment, charge Qc that is emitted from the capacitor 2in the fourth sequence mode M4 is equal to charge Qz that is fed back tothe capacitor 2 in the sixth sequence mode M6. Accordingly, the power isnot take out of the second voltage source. Therefore, it is notnecessary to provide a circuit that supplies the power to the capacitor2 of the second voltage source.

Additionally, the DC power supply 1 of the first voltage source mayoutput voltage E/2 that is half the maximum voltage E necessary foractuators Z1, Z2, Z3, . . . . Accordingly, the power consumption of thedriving device 300 is reduced to a substantial half of the drivingdevice that is charged once to E.

Accordingly, the same effect as the first embodiment is obtained.

Fourth Embodiment

A fourth embodiment will be described with reference to FIGS. 22 to 29.

FIG. 22 is a circuit diagram of a driving device 400 of the fourthembodiment, and only the circuit elements necessary to drive actuator Z1are illustrated in FIG. 22 for the same reason as the second embodiment.The component in common with that of FIG. 13 is designated by the samenumeral.

As illustrated in FIG. 22, the driving device 400 includes a variableswitching power supply 41, a DC power supply 42, a first capacitor 43, asecond capacitor 44, an operational amplifier 45, resistors R1, R2, andR3, N-type channel MOS transistors Q11, Q12, Q21, and Q22, P-typechannel MOS transistors Q13 and Q23, and a switch controller 46.

The switch controller 46 switches between the turn-on and the turn-offof each of MOS transistors Q11, Q12, Q13, Q21, Q22, and Q23. Thevariable switching power supply 41 outputs variable voltage VA/2. The DCpower supply 42 outputs a DC voltage that is larger than the maximumvalue of the variable voltage VA/2, for example, +24 V.

In the fourth embodiment, the capacitances of actuators Z1, Z2, Z3, . .. are substantially equal to one another. The capacitances of the firstand second capacitors 43 and 44 are sufficiently larger than the sum ofthe capacitances of the actuators that can simultaneously be driven inactuators Z1, Z2, Z3, . . . .

The driving device 400 includes first to third power supply lines L1,L2, and L3 and a ground line L0 of 0 V.

The first power supply line L1 is connected to the positive electrode ofthe variable switching power supply 41. The second power supply line L2is connected to the negative electrode of the DC power supply 42. Thepositive electrode of the DC power supply 42 is connected to thenegative electrode of the variable switching power supply 41. The groundline L0 is connected to the connection point of the positive electrodeof the DC power supply 42 and the negative electrode of the variableswitching power supply 41. Accordingly, the second power supply line L2is fixed to potential −24 V.

The first capacitor 43 is connected between the first power supply lineL1 and the ground line L0. The second capacitor 44 is connected betweenthe ground line L0 and the third power supply line L3.

In the operational amplifier 45, a negative input terminal is connectedto the third power supply line L1 through the resistor R1, and apositive input terminal is connected to the ground line L0. An outputterminal of the operational amplifier 45 is connected to the connectionpoint of the resistors R1 and the positive input terminal of theoperational amplifier 45 through the resistor R2. The connection pointof the output terminal of the operational amplifier 45 and the resistorR2 is connected to the power supply line L3 through the resistor R3. Anegative power supply of the operational amplifier 45 is connected tothe second power supply line L2, and a positive power supply isconnected to a low voltage power supply Vcc (for example, +5 V).

In the driving device 400, a series circuit of MOS transistors Q13 andQ11 and a series circuit of MOS transistors Q23 and Q21 areparallel-connected between the first power supply line L1 and the groundline L0.

In the series circuit of MOS transistors Q13 and Q11, the drainelectrodes of MOS transistors Q13 and Q11 are connected to each other.The source electrode of MOS transistor Q13 is connected to the firstpower supply line L1. The source electrode of MOS transistor Q11 isconnected to the ground line L0.

In the series circuit of MOS transistors Q23 and Q21, the drainelectrodes of MOS transistors Q23 and Q21 are connected to each other.The source electrode of MOS transistor Q23 is connected to the firstpower supply line L1. The source electrode of MOS transistor Q21 isconnected to the ground line L0.

In the driving device 400, the drain electrode of MOS transistor Q12 isconnected to the connection point of the drain electrodes of MOStransistors Q13 and Q11. The source electrode of MOS transistor Q12 isconnected to the third power supply line L3.

In the driving device 400, the drain electrode of MOS transistor Q22 isconnected to the connection point of the drain electrodes of MOStransistors Q23 and Q21. The source electrode of MOS transistor Q22 isconnected to the third power supply line L3.

In the driving device 400, the capacitance-type actuator Z1 is connectedbetween the connection point of the drain electrodes of MOS transistorsQ11, Q12, and Q13 and the connection point of the drain electrodes ofMOS transistors Q21, Q22, and Q23.

The back gates of the N-type channel MOS transistors Q11, Q12, Q21, andQ22 are connected to the second power supply line L2 having potential−24 V. The back gates of the P-type channel MOS transistors Q13 and Q23are connected to the first power supply line L1.

The variable switching power supply 41 outputs the first voltage tocharge actuator Z1 (the first voltage source). The first capacitor 43constitutes a buffer of the first voltage source. The second capacitor44 outputs the second voltage to charge actuator Z1 (the second voltagesource).

A circuit 47 including MOS transistors Q11, Q12, Q13, Q21, Q22, and Q23is a charging or discharging individual current-carrying path withrespect to actuators Z1, Z2, Z3, . . . , though in FIG. 22, only theactuator Z1 is illustrated.

A circuit including the operational amplifier 45 and the resistors R1,R2, and R3 is a voltage adjusting circuit 48 that adjusts the voltage ofthe second capacitor 44. The voltage adjusting circuit 48 is what iscalled a linear regulator that charges the second capacitor 44 from thevoltage at the second power supply line L2.

The voltage adjusting circuit 48 of this embodiment is a tracking typelinear regulator that tracks a reverse polarity of a positive potentialvoltage of the first power supply line L1. Alternatively, it may be avariable output linear regulator but is not a tracking type. But it isbetter to select tracking type linear regulator because of thesimplicity. The tracking type regulator is especially suitable whenvariable control of the driving voltage is performed because of itstracking function.

The resistor R1 is equal to the resistor R2 in a resistance value.Accordingly, feedback works such that the output of the operationalamplifier 45 becomes voltage −VA/2 that is equal to the reverse polarityof positive voltage VA/2 applied to the first power supply line L1. Theresistor R3 suppresses an output current of the operational amplifier 45such that a tracking speed is not enhanced beyond necessity. When thetracking speed is enhanced, unnecessary power is consumed.

Accordingly, the third power supply line L3 connected to the negativeelectrode side of the second capacitor 44 becomes potential −VA/2 thattracks the reverse polarity of potential VA/2 at the first power supplyline L1.

The gates of MOS transistors Q11, Q12, Q13, Q21, Q22, and Q23 areconnected to the switch controller 46. The switch controller 46 switchesbetween the turn-on and the turn-off of each of MOS transistors Q11,Q12, Q13, Q21, Q22, and Q23 according to a data table 40 of FIG. 23. Theswitch controller 46 includes a logic circuit. The switch controller 46may include a microcomputer.

In the driving device 400, the turn-on and the turn-off of each of MOStransistors Q11, Q12, Q13, Q21, Q22, and Q23 perform a series ofcharging or discharging sequences to actuator Z1.

A first sequence mode M1 is a waiting state before actuator Z1 ischarged. The switch controller 46 turns on MOS transistors Q11 and Q21and turns off MOS transistors Q12, Q13, Q22, and Q23.

Therefore, as illustrated in FIG. 24, one of the electrodes of actuatorZ1 is connected to the ground line L0 through MOS transistor Q21.Similarly the other electrode of actuator Z1 is connected to the groundline L0 through MOS transistor Q11. Accordingly, in actuator Z1, thepotentials at both ends become 0 V. At this point, the charge voltage ofactuator Z1 is 0 (V).

A second sequence mode M2 is performed immediately before the chargingof actuator Z1 is started, for example, 1 μs before. The switchcontroller 46 turns on MOS transistors Q13 and Q23 and turns off MOStransistors Q11, Q12, Q21, and Q22.

Therefore, as illustrated in FIG. 25, one of the electrodes of actuatorZ1 is connected to the first power supply line L1 through MOS transistorQ23. The other electrode of actuator Z1 is connected to the first powersupply line L1 through MOS transistor Q13. Accordingly, in actuator Z1,the potentials at both ends become VA/2. At this point, the chargevoltage of actuator Z1 is still at 0 (V), and actuator Z1 is notactuated.

A third sequence mode M3 charges actuator Z1. The switch controller 46turns on MOS transistors Q13 and Q21 and turns off MOS transistors Q11,Q12, Q22, and Q23.

Therefore, as illustrated in FIG. 26, a seventh series circuit is formedbetween the first power supply line L1 and the ground line L0. MOStransistor Q13, actuator Z1, and MOS transistor Q21 are series-connectedin the seventh series circuit.

Therefore, the electrode on the side to which MOS transistor Q13 ofactuator Z1 is connected becomes equal to potential VA/2 (V) at thefirst power supply line L1, and the electrode on the side to which MOStransistor Q21 is connected becomes potential 0 (V). Accordingly, acharge Q flows into actuator Z1 from the capacitor 43. As a result,actuator Z1 is charged to voltage VA/2.

A fourth sequence mode M4 further charges actuator Z1. The switchcontroller 46 turns on MOS transistors Q13 and Q22 and turns off MOStransistors Q11, Q12, Q21, and Q23.

Therefore, as illustrated in FIG. 27, an eighth series circuit is formedbetween the first power supply line L1 and the third power supply lineL3. MOS transistor Q13, actuator Z1, and MOS transistor Q22 areseries-connected in the eighth series circuit.

Therefore, the electrode on the side to which MOS transistor Q13 ofactuator Z1 is connected is equal to potential VA/2 (V) at the firstpower supply line L1, and the electrode on the side to which MOStransistor Q22 is connected becomes potential −VA/2 (V) at the thirdpower supply line L3. Accordingly, a charge Qc flows into actuator Z1from the capacitor 43. Charge Qc flows into the negative electrode ofthe capacitor 43 from the positive electrode of the capacitor 44. As aresult, actuator Z1 is charged to voltage VA which is double the voltageof VA/2.

A fifth sequence mode M5 discharges actuator Z1. The switch controller46 turns on MOS transistors Q11 and Q22 and turns off MOS transistorsQ12, Q13, Q21, and Q23.

Therefore, as illustrated in FIG. 28, a ninth series circuit is formedbetween the ground line L0 and the third power supply line L3. MOStransistor Q11, actuator Z1, and MOS transistor Q22 are series-connectedin the ninth series circuit.

The second capacitor 44 had been charged by voltage VA/2. Charge Qz isemitted from actuator Z1 which had been charged by voltage VA. Thenactuator Z1 down to discharged to voltage VA/2.

Charge Qz emitted from actuator Z1 is fed back to the second capacitor44 through MOS transistor Q11.

The capacitances of the capacitors 43 and 44 are sufficiently largerthan the sum of the capacitances of the actuators that cansimultaneously be driven in actuators Z1, Z2, Z3, . . . . Therefore,even if charges Q, Qc, and Qz are emitted, the charge voltages of thecapacitors 43 and 44 are substantially maintained at voltage VA/2. So,charge Qz fed back to the second capacitor 44 is equal to charge Qc thatis emitted from the second capacitor 44 in the last fourth sequence modeM4.

A sixth sequence mode M6 further discharges actuator Z1. The switchcontroller 46 turns on MOS transistors Q11 and Q21 and turns off MOStransistors Q12, Q13, Q22, and Q23.

Therefore, a fifteenth closed circuit is formed as illustrated in FIG.29. The fifteenth closed circuit connects the electrodes of actuator Z1through MOS transistors Q11 and Q21. Accordingly, the charge is furtheremitted from actuator Z1, and actuator Z1 is discharged until thevoltage becomes 0 (V).

MOS transistors Q11, Q12, Q13, Q21, Q22, and Q23 are turned on and offaccording to the series of charging or discharging sequences of thefirst to sixth sequence modes M1, M2, M3, M4, M5, and M6. Therefore,actuator Z1 is charged or discharged.

In the fourth embodiment, voltage change for the actuator Z1 betweeneach sequence steps M2→M3, M3→M4, M4→M5, and M5→M6 are all VA/2 (V), soQ=Qc=Qz. Accordingly the first capacitor 43 lacks charge 2Q through allthe sequences. The deficit of charge 2Q is supplied from the positiveelectrode of the variable switching power supply 41. Consumption energyrelating to one series of sequence of the driving device 400 is obtainedby multiplying the deficit of charge 2Q by the output voltage VA/2 ofthe variable switching power supply 41.

On the other hand, charge Q (=Qc) is emitted from the positive electrodeof the second capacitor 44 in the fourth sequence mode M4, and the samecharge Q (=Qz) is fed back to the second capacitor 44 in the fifthsequence mode M5. The charge that flows into and out from the secondcapacitor 44 becomes zero through the whole sequence.

In the driving device 400, it is necessary to charge the secondcapacitor 44 with a relatively large charge only in the first time afterthe power-on. Generally a certain level of waiting time is allowablejust after the power-on. Therefore, there is no problem to wait for thevoltage adjusting circuit 48 to charge the second capacitor 44 tovoltage VA/2.

In the fourth embodiment, charge Qc that is emitted from the secondcapacitor 44 in the fourth sequence mode M4 is equal to charge Qz thatis fed back to the second capacitor 44 in the fifth sequence mode M5.Additionally, the variable switching power supply 41 may output voltageVA/2 that is half maximum voltage VA necessary for actuator Z1.Accordingly, the same effect as the first embodiment is obtained.

The DC power supply 42 has no relation with the driving power ofactuator Z1. The power consumption of the DC power supply 42 issignificantly smaller than the power for driving the actuator.

Fifth Embodiment

A fifth embodiment will be described with reference to additional FIGS.30 to 34.

In the fourth embodiment, the electrode on the side to which MOStransistor Q13 of actuator Z1 is connected is equal to the potentialVA/2 at the first power supply line L1 in the third sequence mode M3(FIG. 26). Accordingly, actuator Z1 is charged by voltage VA/2.

In the fifth embodiment, contrary to the fourth embodiment, theelectrode on the opposite side to an actuator Z1 is set to the positiveelectrode so as to be equal to potential VA/2 at a first power supplyline L1. Actuator Z1 is also discharged by voltage VA/2.

A driving device of the fifth embodiment is identical to the drivingdevice 400 of the fourth embodiment except for the sequence control.Thereby, FIG. 22 and its explanation in the forth embodiment issubstituted for the description of the configuration of the drivingdevice of the fifth embodiment.

In the case in which the charge direction of actuator Z1 is inverted,the method for driving each ink channel of the individualcurrent-carrying path may simply be replaced as described in the firstembodiment. However, in the fifth embodiment, another method forinverting the charge direction will be described.

In the fifth embodiment, a switch controller 46 switches between theturn-on and the turn-off of each of MOS transistors Q11, Q12, Q13, Q21,Q22, and Q23 according to a data table 50 of FIG. 30. Thereby, thedriving device 400 performs a series of charging or dischargingsequences to actuator Z1.

A first sequence mode M1 is a waiting state before actuator Z1 ischarged. The switch controller 46 turns on MOS transistors Q11 and Q21and turns off MOS transistors Q12, Q13, Q22, and Q23. The first sequencemode M1 of the fifth embodiment is identical to the first sequence modeM1 of the fourth embodiment.

Thereby, as illustrated in FIG. 24, one of the electrodes of actuator Z1is connected to a ground line L0 through MOS transistor Q21. Similarlythe other electrode of actuator Z1 is connected to the ground line L0through MOS transistor Q11. Accordingly, in actuator Z1, the potentialsat both ends are 0 (V). Thereby charged voltage of the actuator Z1 is 0(V).

A second sequence mode M2 charges actuator Z1. The switch controller 46turns on MOS transistors Q11 and Q23 and turns off MOS transistors Q12,Q13, Q21, and Q22.

Thereby, as illustrated in FIG. 31, a tenth series circuit is formedbetween the first power supply line L1 and the ground line L0. MOStransistor Q23, actuator Z1, and MOS transistor Q11 are series-connectedin the tenth series circuit.

Thereby, the electrode on the side to which MOS transistor Q23 ofactuator Z1 is connected becomes equal to potential VA/2 at the firstpower supply line L1, and the electrode on the side to which MOStransistor Q11 is connected becomes potential 0 (V). Accordingly, acharge Q flows into actuator Z1 from a capacitor 43. As a result,actuator Z1 is charged to voltage VA/2.

A third sequence mode M3 further charges actuator Z1. The switchcontroller 46 turns on MOS transistors Q12 and Q23 and turns off MOStransistors Q11, Q13, Q21, and Q22.

Thereby, as illustrated in FIG. 32, an eleventh series circuit is formedbetween the first power supply line L1 and a third power supply line L3.MOS transistor Q23, actuator Z1, and MOS transistor Q12 areseries-connected in the eleventh series circuit.

Thereby, the electrode on the side to which MOS transistor Q23 ofactuator Z1 is connected becomes equal to potential VA/2 at the firstpower supply line L1, and the electrode on the side to which MOStransistor Q12 is connected becomes potential −VA/2 at the third powersupply line L3. Accordingly, a charge Qc flows into actuator Z1 from thecapacitor 43. As a result, actuator Z1 is charged to voltage VA which isdouble the voltage of VA/2. At this point, charge Qc flows into thenegative electrode of the first capacitor 43 from a positive electrodeof a second capacitor 44.

A fourth sequence mode M4 discharges actuator Z1. The switch controller46 turns on MOS transistors Q12 and Q21 and turns off MOS transistorsQ11, Q13, Q22, and Q23.

Thereby, as illustrated in FIG. 33, a twelfth series circuit is formedbetween the ground line L0 and the third power supply line L3. MOStransistor Q12, actuator Z1, and MOS transistor Q21 are series-connectedin the twelfth series circuit.

The second capacitor 44 between the ground line L0 and the third powersupply line L3 is charged. Accordingly, a charge Qz is emitted fromactuator Z1 which had been charged by voltage VA. Then actuator Z1 isdischarged to voltage VA/2.

Charge Qz emitted from actuator Z1 is fed back to the second capacitor44 through MOS transistor Q21.

The capacitances of the capacitors 43 and 44 are sufficiently largerthan the sum of the capacitances of the actuators that cansimultaneously be driven in actuators Z1, Z2, Z3, . . . . Therefore,even if charges Q, Qc, and Qz are emitted or fed back, the chargevoltages of the capacitors 43 and 44 are substantially maintained atvoltage VA/2. Therefore, charge Qz fed back to the second capacitor 44is equal to the charge Qc that is emitted from the second capacitor 44in the last third sequence mode M3.

A fifth sequence mode M5 further discharges actuator Z1. The switchcontroller 46 turns on MOS transistors Q11 and Q21 and turns off MOStransistors Q12, Q13, Q22, and Q23.

Thereby, a sixteenth closed circuit is formed as illustrated in FIG. 34.The sixteenth closed circuit connects each electrode of actuator Z1through MOS transistors Q21 and Q11.

Accordingly, the charge is further emitted from actuator Z1. Actuator Z1is discharged to voltage 0 V.

Thus MOS transistors Q11, Q12, Q13, Q21, Q22, and Q23 are turned on andoff according to the series of charging or discharging sequences of thefirst to fifth sequence modes M1, M2, M3, M4, and M5. Thereby, actuatorZ1 is charged or discharged.

In the fifth embodiment, voltage change for the actuator Z1 between eachsequence steps M2→M3, M3→M4, M4→M5, and M5→M6 are all VA/2 (V), soQ=Qc=Qz. Accordingly the first capacitor 43 lacks charge 2Q through allthe sequences. The deficit of charge 2Q is supplied from the positiveelectrode of the variable switching power supply 41. Consumption energyrelating to one series of sequence of the driving device 400 is obtainedby multiplying the deficit of charge 2Q by the output voltage VA/2 ofthe variable switching power supply 41.

On the other hand, charge Q (=Qc) is emitted from the positive electrodeof the second capacitor 44 in the third sequence mode M3, and the samecharge Q (=Qz) is fed back to the second capacitor 44 in the fourthsequence mode M4. The charge that flows into and out from the secondcapacitor 44 becomes zero through the whole sequence.

In the driving device 400, it is necessary to charge the secondcapacitor 44 with a relatively large charge only in the first time afterthe power-on. Generally a certain level of waiting time is allowablejust after the power-on. Therefore, there is no problem to wait for thevoltage adjusting circuit 48 to charge the second capacitor 44 tovoltage VA/2.

In the fifth embodiment, respective modes of M1 through M5 arecontrolled so that charge Qc that is emitted from the second capacitor44 in the third sequence mode M3 is equal to charge Qz that is fed backto the second capacitor 44 in the fourth sequence mode M4. This controlsystem causes the second voltage source not to consume the electricpower. Therefore, the capacitor 44, i.e., the second voltage source, isnot needed to supply the electric power. Thus, even if a small powerlinear regulator, i.e., a voltage adjusting circuit 48 which is composedof a small power operational amplifier 45 and resistances R1, R2, andR3, is applied to the control system, a voltage potential of the powersupply line L3 can be sufficiently stabilized. Additionally, thevariable switching power supply 41 may output voltage VA/2 that is halfmaximum voltage VA necessary for actuator Z1. Accordingly, the sameeffect as the first embodiment is obtained.

The DC power supply 42 has no relation with the driving power ofactuator Z1. The DC power supply 42 only biases a back-gate of theN-type channel MOS transistors Q11, Q12, Q21, and Q22 and serves as anegative power line for an operational amplifier 45. Therefore, thepower consumption of the DC power supply 42 is significantly smallerthan the power for driving the actuator.

The same effect as the fourth embodiment is obtained in the fifthembodiment.

In the fifth embodiment, the method for driving each ink channel of theindividual current-carrying path may simply be replaced as described inthe first embodiment. In such cases, the charging and discharging areperformed in the same direction as in the fourth embodiment.

In the actuator for the inkjet head, the proper driving voltage variesaccording to viscosity of the ink. The viscosity of the ink variesaccording to a kind of the ink or a temperature of the ink.Characteristics of the actuator also have variations and temperaturecharacteristics. Therefore, from various viewpoints, desirably thedriving voltage can be changed to properly drive the actuator.

In the fourth and fifth embodiments, the charge voltage of the capacitor44 that is of the second voltage source automatically tracks the powersupply voltage of the first voltage source. Therefore, advantageouslythe adjustment can simply be made, and accuracy of the adjustment of thedrive voltage for the actuator can be improved.

Other Embodiments

In the fourth and fifth embodiments, the variable switching power supply41 is used as the first voltage source. The variable switching powersupply may be used as the first voltage source 1 in the first, second,and third embodiments.

In the first, second, and third embodiments, the charge voltage of thecapacitor 2 that is of the second voltage source is directly chargedfrom the first voltage source. Accordingly, the voltage at the secondvoltage source tracks the voltage at the first voltage source even ifthe special control is not performed.

That is, in all the embodiments, the voltage at the second voltagesource tracks the voltage at the first voltage source. In the drivingdevice of the embodiments, the voltages at the voltage sources on thepositive and negative electrode sides can simultaneously be adjusted byadjusting one driving voltage.

In the fourth and fifth embodiments, the first capacitor 43 is providedas the buffer in parallel to the first voltage source. Alternatively,the first voltage source may have a function of the buffer.

In the first, second, and third embodiments, the buffer is not shown inparallel to the first voltage source. Alternatively, similarly to thefourth and fifth embodiments, the capacitor may be provided as thebuffer in parallel to the first voltage source.

In the first embodiment, the inkjet head is the shear-mode, shared-walltype in which the actuator is shared by the adjacent ink channels. Inthe second to fifth embodiment, the description is focused tocharge/discharge function but not very detail of how to eject the ink.But the inkjet head may be either a shared wall type or anon-shared-wall type in which a piezoelectric actuator is not shared bythe adjacent ink channels but is provided with each ink channel to ejectink through a nozzle arranged to the each ink channel. In the first tofifth embodiments, either the shared wall type or the non-shared walltype inkjet head can be applied. The embodiments can widely be appliedto the actuator that is driven by the charging and discharging.

In all the embodiments, when the operation to drive a terminal of eachactuator in the individual driving circuit is replaced with theoperation to drive another terminal of each actuator in the individualdriving circuit, the charging and discharging can be performed in theopposite direction to that of the embodiments.

Alternatively all the P-type channel transistors may be replaced withthe N-type channel transistors while all the N-type channel transistorsmay be replaced with the P-type channel transistors, and also thepolarities of all the power supplies and capacitors may be inverted.Thereby, the charging and discharging may be performed in the oppositedirection to that of the embodiments.

Alternatively, the charging and discharging may be performed in the samedirection as the embodiments by simultaneously performing both.

In the embodiments, assuming that 400 actuators are simultaneouslydriven while each actuator has a capacitance of 250 pF, the sum ofcapacitances maximally becomes 0.1 μF. In this case, it is necessarythat the capacitor 2 of the first, second, and third embodiments and thecapacitors 43 and 44 of the fourth and fifth embodiments be sufficientlylarger than 0.1 μF, so that the capacitor 2 and the capacitors 43 and 44may be set to 10 μF, which is 100 times the sum of capacitances.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. An apparatus for driving a capacitance-type actuator comprising: afirst voltage source that outputs a first voltage to charge theactuator; a second voltage source that outputs a second voltage tocharge the actuator; and a driver that switches among a first charge, asecond charge, a first discharge, and a second discharge, the firstvoltage output from the first voltage source being supplied to theactuator in the first charge, a sum of the first voltage output from thefirst voltage source and the second voltage output from the secondvoltage source being supplied to the actuator in the second charge, acharge accumulated in the actuator by the first and second charges beingemitted and guided to the second voltage source in the first discharge,the charge accumulated in the actuator being emitted without guiding thecharge to the second voltage source in the second discharge.
 2. Theapparatus of claim 1, wherein a charge output from the second voltagesource by the second charge is equal to a charge guided to the secondvoltage source by the first discharge.
 3. The apparatus of claim 2,wherein the second voltage source is a capacitor, and a capacitance ofthe capacitor is sufficiently larger than a capacitance of the actuator.4. The apparatus of claim 3, further comprising a charge pump circuitthat parallel-connects the first voltage source and the capacitor tocharge the capacitor and series-connects the first voltage source andthe capacitor to output a voltage double a voltage output from the firstvoltage source.
 5. The apparatus of claim 3, further comprising avoltage adjusting circuit that adjusts a charge voltage of thecapacitor.
 6. The apparatus of claim 5, wherein the voltage adjustingcircuit is a linear regulator that generates a voltage to charge thecapacitor from a voltage at a power supply line connected to a negativeelectrode of a DC power supply.
 7. The apparatus of claim 5, wherein thevoltage adjusting circuit is a tracking regulator that tracks of areverse polarity of a potential at a power supply line connected to apositive electrode of the first voltage source.
 8. The apparatus ofclaim 1, wherein the driver switches among a first sequence mode, asecond sequence mode, a third sequence mode, and a fourth sequence mode,the first voltage output from the first voltage source being supplied tothe actuator to charge the actuator in the first sequence mode, the sumof the first voltage output from the first voltage source and the secondvoltage output from the second voltage source being supplied to theactuator to further charge the actuator in the second sequence mode, thecharge accumulated in the actuator being emitted so as to be guided tothe second voltage source and the actuator being discharged in the thirdsequence mode, the charge accumulated in the actuator being emittedwithout guiding the charge to the second voltage source and the actuatorbeing discharged in the fourth sequence mode.
 9. The apparatus of claim8, wherein the driver sets a potential at a negative electrode of theactuator to 0 V before the first sequence mode is performed.
 10. Amethod for driving a capacitance-type actuator comprising: supplying afirst voltage output from a first voltage source to the actuator tocharge the actuator; supplying a sum of the first voltage output fromthe first voltage source and a second voltage output from a secondvoltage source to the actuator to further charge the actuator; emittinga charge accumulated in the actuator so as to guide the charge to thesecond voltage source and discharging the actuator; and emitting thecharge accumulated in the actuator without guiding the charge to thesecond voltage source and further discharging the actuator.
 11. Themethod of claim 10, wherein a charge output from the second voltagesource in supplying the sum of the first voltage and the second voltageto the actuator to charge the actuator is equalized with a charge guidedto the second voltage source in emitting the charge accumulated in theactuator so as to guide the charge to the second voltage source anddischarging the actuator.
 12. The method of claim 10, wherein the secondvoltage source is a capacitor, and a capacitance of the capacitor issufficiently larger than a capacitance of the actuator.
 13. The methodof claim 12, wherein the first voltage source is parallel-connected tothe capacitor to charge the capacitor and series-connected to thecapacitor to supply a voltage double an output voltage to the actuator.14. The method of claim 12, wherein a charge voltage of the capacitor isadjusted by a voltage adjusting circuit.
 15. The method of claim 14,wherein the voltage adjusting circuit is a linear regulator thatgenerates a voltage to charge the capacitor from a voltage at a powersupply line connected to a negative electrode of a DC power supply. 16.The method of claim 14, wherein the voltage adjusting circuit is atracking regulator that tracks of a reverse polarity of a potential at apower supply line connected to a positive electrode of the first voltagesource.
 17. The method of claim 10, wherein a first sequence mode, asecond sequence mode, a third sequence mode, and a fourth sequence modeare sequentially performed, the first voltage output from the firstvoltage source being supplied to the actuator to charge the actuator inthe first sequence mode, the sum of the first voltage output from thefirst voltage source and the second voltage output from the secondvoltage source being supplied to the actuator to further charge theactuator in the second sequence mode, the charge accumulated in theactuator being emitted so as to be guided to the second voltage sourceand the actuator being discharged in the third sequence mode, the chargeaccumulated in the actuator being emitted without guiding the charge tothe second voltage source and the actuator being discharged in thefourth sequence mode.
 18. The method of claim 17, wherein a potential ata negative electrode of the actuator is set to 0 V before the firstsequence mode is performed.